Amos’s name day is June 15, the feast of Amos the Prophet.
Churches that follow the Old (Julian) Calendar keep the same feast on June 28 of the civil calendar. See everything commemorated on June 15.
The saint behind the name

Amos the Prophet
June 15, Prophet, Αμώς
The Holy Prophet Amos was a shepherd and dresser of sycamore trees from Tekoa, called by God in the eighth century before Christ to prophesy to the northern kingdom of Israel. A plain man with no schooling of the prophets, he spoke fearlessly against the injustice of the rich and the emptiness of worship without righteousness, declaring the word of the Lord: let justice roll down like waters.
Name days: Amos
What to say on a name day
The Greek wish is Χρόνια Πολλά (Chronia Polla), “many years.” A call or a short message on the day is what people remember. See name day wishes you can send and what a name day is.